The Exposure Assessment Core will be responsible for collecting data to enable estimates of exposures for the three health studies. This will include: 1) collecting and quality checking routine air monitoring data from the Air Resources Board; 2) establishing sampling for polycyclic aromatic hydrocarbons (PAHs) and endotoxin at a central site in Bakersfield and collecting and analyzing samples there for one year to establish the temporal variability for PAHs and endotoxin; 3) collecting contemporaneous samples for PAHs and endotoxin at multiple locations for 1-2 months; 4) exploring the varying spatial patterns for routine air pollutants, PAHs and endotoxin. The data for routinely collected pollutants are needed to understand current exposure gradients in the communities, which will differ by air contaminant, and to facilitate health effects analyses for Project 3. The PM2.5 chemical constituents will include elemental carbon, organic carbon, nitrate, sulfate, and trace metals. In addition, PAH data will be collected at two other air monitoring stations for a 2 month period in fall/winter 2010/201 land endotoxin samples will be collected at 5 other air monitoring stations for a 1 month period in summer 2010. These are being collected to improve the understanding of spatial variability of these pollutants in the greater Bakersfield area which is critical to the design of the center. No spatial data of this type currently exist for this area. These exposure data will be used by the health studies as part of their planned work for the pre-center, but will also guide us in planning the data the center will need to collect when it is a full center.